The presently disclosed embodiments relate generally to layers that are useful in imaging apparatus members and components, for use in electrophotographic, including digital printing, apparatuses. More particularly, the embodiments pertain to an improved electrophotographic imaging member comprising a very thin outer layer on the imaging member surface, where the outer layer comprises functional materials that act as a lubricant and or a barrier against moisture and/or surface contaminants to address high torque and A-zone deletion. The very thin outer layer is applied to the imaging member on a nano-scale or molecular level. The improved imaging member exhibits improved xerographic performance, such as improved interaction with the blade cleaner and reduced image deletions in high humidity conditions. The embodiments also pertain to methods and systems for delivering the materials to the surface of the imaging member.
In electrophotographic or electrophotographic printing, the charge retentive surface, typically known as a photoreceptor, is electrostatically charged, and then exposed to a light pattern of an original image to selectively discharge the surface in accordance therewith. The resulting pattern of charged and discharged areas on the photoreceptor form an electrostatic charge pattern, known as a latent image, conforming to the original image. The latent image is developed by contacting it with a finely divided electrostatically attractable powder known as toner. Toner is held on the image areas by the electrostatic charge on the photoreceptor surface. Thus, a toner image is produced in conformity with a light image of the original being reproduced or printed. The toner image may then be transferred to a substrate or support member (e.g., paper) directly or through the use of an intermediate transfer member, and the image affixed thereto to form a permanent record of the image to be reproduced or printed. Subsequent to development, excess toner left on the charge retentive surface is cleaned from the surface. The process is useful for light lens copying from an original or printing electronically generated or stored originals such as with a raster output scanner (ROS), where a charged surface may be imagewise discharged in a variety of ways.
The described electrophotographic copying process is well known and is commonly used for light lens copying of an original document. Analogous processes also exist in other electrophotographic printing applications such as, for example, digital laser printing or ionographic printing and reproduction where charge is deposited on a charge retentive surface in response to electronically generated or stored images.
Scorotron has been employed to charge the surface of a photoreceptor. Alternatively, to charge the surface of a photoreceptor, a contact type charging device has been used, such as disclosed in U.S. Pat. No. 7,580,655, which is incorporated herein by reference. The contact type charging device, also termed “bias charge roll” (BCR) includes a conductive member which is supplied a voltage from a power source with a D.C. voltage superimposed with an A.C. voltage of no less than twice the level of the D.C. voltage. The charging device contacts the image bearing member (photoreceptor) surface, which is a member to be charged. The outer surface of the image bearing member is charged by contact with the BCR. The contact type charging device charges the image bearing member to a predetermined potential. Typically the contact type charger is in the form of a roll charger such as that disclosed in U.S. Pat. No. 4,387,980, which is incorporated herein by reference. Further, a vicinity type of charging roller may also be suitable to charge a photoreceptor surface, such as in U.S. Pat. No. 6,360,065, which is incorporated herein by reference.
Electrophotographic photoreceptors can be provided in a number of forms. For example, the photoreceptors can be a homogeneous layer of a single material, such as vitreous selenium, or it can be a composite layer containing a photoconductive layer and another material. In addition, the photoreceptor can be layered. Multilayered photoreceptors or imaging members have at least two layers, and may include a substrate, a conductive layer, an optional undercoat layer (sometimes referred to as a “charge blocking layer” or “hole blocking layer”), an optional adhesive layer, a photogenerating layer (sometimes referred to as a “charge generation layer,” “charge generating layer,” or “charge generator layer”), a charge transport layer, and an optional overcoating layer in either a flexible belt form or a rigid drum configuration. In the multilayer configuration, the active layers of the photoreceptor are the charge generation layer (CGL) and the charge transport layer (CTL). Enhancement of charge transport across these layers provides better photoreceptor performance. Multilayered flexible photoreceptor members may include an anti-curl layer on the backside of the substrate, opposite to the side of the electrically active layers, to render the desired photoreceptor flatness.
Conventional photoreceptors are disclosed in the following patents, a number of which describe the presence of light scattering particles in the undercoat layers: Yu, U.S. Pat. No. 5,660,961; Yu, U.S. Pat. No. 5,215,839; and Katayama et al, U.S. Pat. No. 5,958,638. The term “photoreceptor” or “photoconductor” is generally used interchangeably with the terms “imaging member.” The term “electrophotographic” includes “electrophotographic” and “xerographic.” The terms “charge transport molecule” are generally used interchangeably with the terms “hole transport molecule.”
To further increase the service life of the photoreceptor, use of overcoat layers has also been implemented to protect photoreceptors and improve performance, such as wear resistance. However, these low-wear overcoats are associated with poor image quality due to A-zone deletion in a humid environment as the wear rates decrease to a certain level. In addition, high torque associated with low-wear overcoats in A-zone also cause severe issues with BCR charging systems, such as motor failure and blade damage. As a result, use of a low wear overcoat with BCR charging systems is still a big challenge, and there is a need to find a way to achieve the life target with overcoat technology in such systems.